A power converter includes a transformer, a resonant capacitor, a high-side transistor, a low-side transistor, a rectification circuit, a feedback circuit, a detection circuit, and a control circuit. The transformer includes a primary coil coupled to a switch node and a secondary coil. The resonant capacitor is coupled to the primary coil. The high-side transistor provides an input voltage to the switch node, and the low-side transistor couples the switch node to the ground. The rectification circuit converts the energy of the secondary coil into an output voltage. The feedback circuit compares the output voltage with a reference voltage to generate a compensation signal. The detection circuit generates a current detection signal and a voltage detection signal. The control circuit drives the high-side transistor and the low-side transistor based on the current detection signal, the voltage detection signal, the compensation signal, and the input signal.
Legal claims defining the scope of protection, as filed with the USPTO.
. A power conversion circuit, comprising:
. The power conversion circuit as claimed in, wherein the detection circuit detects a current flowing through the resonant capacitor to generate the current detection signal;
. The power conversion circuit as claimed in, wherein the control circuit comprises:
. The power conversion circuit as claimed in, wherein the control circuit comprises:
. The power conversion circuit as claimed in, wherein the threshold voltage is determined based on half of the input voltage.
. The power conversion circuit as claimed in, wherein the rectification circuit comprises:
. The power conversion circuit as claimed in, wherein the voltage detection signal is close to the threshold voltage;
. The power conversion circuit as defined in, wherein the control circuit comprises:
. The power conversion circuit as defined in, wherein when the low-side transistor is turned off and a dead time has passed, the high-side transistor is turned on to achieve zero voltage switching.
. The power conversion circuit as defined in, wherein when the high-side transistor is turned off and a dead time has passed, the low-side transistor is turned on to achieve zero voltage switching.
. The power conversion circuit as defined in, wherein the detection circuit comprises a resistor and a capacitor;
. The power conversion circuit as defined in, wherein the detection circuit further comprises:
. The power conversion circuit as defined in, wherein the detection circuit comprises:
. The power conversion circuit as defined in, wherein the detection circuit comprises:
. A control method adapted to control a power conversion circuit, wherein the power conversion circuit comprises a resonant capacitor between a resonant node and a ground, a transformer comprising a primary coil and a secondary coil, a high-side transistor providing an input voltage to a switch node, a low-side transistor coupling the switch node to the ground, and a rectification circuit converting energy of the secondary coil into an output voltage, wherein the primary coil is coupled between the switch node and the resonant node, wherein the control method comprises the following steps:
. The control method as claimed in, wherein the control method further comprises the following steps:
. The control method as claimed in, wherein when the low-side transistor is turned off and a dead time has passed, the high-side transistor is turned on to achieve zero voltage switching.
. The control method as claimed in, wherein when the high-side transistor is turned off and a dead time has passed, the low-side transistor is turned on to achieve zero voltage switching.
. The control method as claimed in, wherein the threshold voltage is determined based on half of the input voltage.
. The control method as claimed in, wherein the rectification circuit comprises an output capacitor, a first rectification unit generating a first current, and a second rectification unit generating a second current;
Complete technical specification and implementation details from the patent document.
This application claims the benefit of U.S. Provisional Application No. 63/647,125, filed on May 14, 2024, the entirety of which is incorporated by reference herein.
This application claims priority of Taiwan Patent Application No. 114101621, filed on Jan. 15, 2025, the entirety of which is incorporated by reference herein.
The disclosure is generally related to a power conversion circuit and a control method thereof, and more particularly it is related to a power conversion circuit and a control method thereof that drives the high-side transistor and the low-side transistor by using the current flowing through the resonant capacitor, the voltage across the resonant capacitor, a compensation signal, and an input voltage.
With the continuous advancements being made in portable electronic devices, the development of power conversion circuits, like most power products, is trending in the direction of high efficiency, high power density, high reliability, and low cost. A resonant power conversion circuit (including LLC resonant power conversion circuit, etc.) has the advantages of achieving zero-voltage switching (ZVS) on the primary side and zero-current switching (ZCS) of the rectification diode on the secondary side within the full load range, causing the duty cycles of the high-side and low-side transistors to both be 50% by frequency control. No output inductor is required, and low-voltage transistors can be used on the secondary side. This leads to cost reductions and efficiency improvements. The resonant power conversion circuit has been increasingly used for DC voltage conversion in recent years.
However, due to the circuit characteristics of the resonant power conversion circuit, a higher switching frequency must be used when the output voltage is low or the load is light, resulting in poor conversion efficiency of the resonant power conversion circuit. In order to meet the current market demand for a wide range of output voltages, high output power, and high conversion efficiency, it is necessary to further optimize the power conversion circuit to meet market demand.
The present invention proposes a power conversion circuit and a control method thereof, so that the LLC resonant power conversion circuit has a wider output voltage range and also achieves zero voltage switching to reduce switching power loss. In addition, the power conversion circuit and control method thereof proposed in the present invention can detect the voltage of the switch node and turn on the low-side transistor when the voltage is relatively low, which helps to further reduce power loss. Furthermore, the voltage across the resonant capacitor can be adjusted by adjusting the threshold voltage, thereby balancing the currents flowing through the rectification units to reduce the ripple of the output voltage. The lower ripple of the output voltage allows the use of a smaller output capacitor.
In an embodiment, a power conversion circuit comprises a transformer, a resonant capacitor, a high-side transistor, a low-side transistor, a rectification circuit, a feedback circuit, a detection circuit, and a control circuit. The transformer comprises a primary coil and a secondary coil, wherein the primary coil is coupled between a switch node and a resonant node. The resonant capacitor is coupled between the resonant node and a ground. The high-side transistor provides an input voltage to the switch node based on a high-side driving signal. The low-side transistor couples the switch node to the ground based on a low-side driving signal. The rectification circuit converts the energy of the secondary coil into an output voltage. The feedback circuit compares the output voltage with a reference voltage to generate a compensation signal. The detection circuit is coupled to the resonant node to generate a current detection signal and a voltage detection signal. The control circuit generates the high-side driving signal and the low-side driving signal based on the current detection signal, the voltage detection signal, the compensation signal, and the input voltage. When the high-side transistor is turned on and the current detection signal exceeds the compensation signal, the control circuit turns off the high-side transistor. When the voltage detection signal does not exceed a threshold voltage, the control circuit turns off the low-side transistor.
According to an embodiment of the present invention, the detection circuit detects a current flowing through the resonant capacitor to generate the current detection signal. The voltage detection signal is related to a voltage across the resonant capacitor.
According to an embodiment of the present invention, the control circuit comprises a first comparator. The first comparator compares the current detection signal and the compensation signal to generate an output signal. The control circuit turns off the high-side transistor based on the output signal.
According to an embodiment of the present invention, the control circuit comprises a second comparator. The second comparator compares the voltage detection signal and the threshold voltage to generate an output signal. The control signal turns off the low-side transistor based on the output signal, thereby reducing a ripple of the output voltage.
According to an embodiment of the present invention, the threshold voltage is determined based on half of the input voltage.
According to an embodiment of the present invention, the rectification circuit comprises an output capacitor, a first rectification unit, and a second rectification unit. The first rectification unit regulates the energy of the secondary coil to generate a first current. The second rectification unit regulates the energy of the secondary coil to generate a second current. The first current and the second current are configured to charge the output capacitor to generate the output voltage. A direction of the first current is to the same as a direction of the second current.
According to an embodiment of the present invention, the voltage detection signal is close to the threshold voltage. When the voltage detection signal is close to half of the input voltage, magnitude of the first current is close to magnitude of the second current, thereby reducing a ripple of the output voltage.
According to an embodiment of the present invention, the control circuit comprises a valley-voltage detection circuit. The valley-voltage detection circuit is configured to detect a voltage across the low-side transistor at a relatively low point to generate a valley signal. The control circuit turns on the low-side transistor based on the valley signal, so as to reduce switching power loss of the low-side transistor.
According to an embodiment of the present invention, when the low-side transistor is turned off and a dead time has passed, the high-side transistor is turned on to achieve zero voltage switching.
According to an embodiment of the present invention, when the high-side transistor is turned off and a dead time has passed, the low-side transistor is turned on to achieve zero voltage switching.
According to an embodiment of the present invention, the detection circuit comprises a resistor and a capacitor. The resistor and the capacitor are connected in series between the resonant node and the ground. A voltage across the resistor is the current detection signal.
According to an embodiment of the present invention, the detection circuit further comprises an integrator. The integrator integrates the current detection signal to generate the voltage detection signal.
According to an embodiment of the present invention, the detection circuit comprises a detection resistor. The detection resistor is coupled between the resonant capacitor and the ground. A voltage across the detection resistor is the current detection signal.
According to an embodiment of the present invention, the detection circuit comprises a capacitance voltage-dividing circuit. The capacitance voltage-dividing circuit is coupled to both terminals of the resonant capacitor. The capacitance voltage-dividing circuit is configured to divide a voltage across the resonant capacitor to generate the voltage detection signal.
In another embodiment, a control method adapted to control a power conversion circuit is provided. The power conversion circuit comprises a resonant capacitor between a resonant node and a ground, a transformer comprising a primary coil and a secondary coil, a high-side transistor providing an input voltage to a switch node, a low-side transistor coupling the switch node to the ground, and a rectification circuit converting energy of the secondary coil into an output voltage. The primary coil is coupled between the switch node and the resonant node. the control method comprises the following steps. The output voltage is compared with a reference voltage to generate a compensation signal. A current detection signal is generated based on a current flowing through the resonant capacitor. A voltage detection signal related to a voltage across the resonant capacitor is generated. The high-side transistor and the low-side transistor are driven based on the current detection signal, the voltage detection signal, the compensation signal, and the input voltage. When the high-side transistor is turned on and the current detection signal exceeds the compensation signal, the high-side transistor is turned off. When the voltage detection signal does not exceed a threshold, the low-side transistor is turned off.
According to an embodiment of the present invention, the control method further comprises the following steps. A voltage across the low-side transistor is detected. When the voltage across the low-side transistor is a valley voltage, the low-side transistor is turned on, thereby reducing switching power loss of the low-side transistor.
According to an embodiment of the present invention, when the low-side transistor is turned off and a dead time has passed, the high-side transistor is turned on to achieve zero voltage switching.
According to an embodiment of the present invention, when the high-side transistor is turned off and a dead time has passed, the low-side transistor is turned on to achieve zero voltage switching.
According to an embodiment of the present invention, the threshold voltage is determined based on half of the input voltage.
According to an embodiment of the present invention, the rectification circuit comprises an output capacitor, a first rectification unit generating a first current, and a second rectification unit generating a second current. The first current and the second current charge the output capacitor to generate the output voltage. The voltage detection signal is close to the threshold voltage. When the voltage detection signal is close to half of the input voltage, magnitude of the first current is close to magnitude of the second current, so as to reduce a ripple of the output voltage.
A detailed description is given in the following embodiments with reference to the accompanying drawings.
The following description is made for the purpose of illustrating the general principles of the disclosure and should not be taken in a limiting sense. The scope of the disclosure is determined by reference to the appended claims.
In the following detailed description, for purposes of explanation, numerous specific details and embodiments are set forth in order to provide a thorough understanding of the present disclosure. The use of like and/or corresponding numerals in the drawings of different embodiments does not suggest any correlation between different embodiments.
In addition, in some embodiments of the present disclosure, terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly (for example, electrically connection) via intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.
In addition, in this specification, relative spatial expressions are used. For example, “lower”, “bottom”, “higher” or “top” are used to describe the position of one element relative to another. It should be appreciated that if a device is flipped upside down, an element that is “lower” will become an element that is “higher”.
It should be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers, portions and/or sections, these elements, components, regions, layers, portions and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, portion or section from another element, component, region, layer or section. Thus, a first element, component, region, layer, portion or section in the specification could be termed a second element, component, region, layer, portion or section in the claims without departing from the teachings of the present disclosure.
It should be understood that this description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. The drawings are not drawn to scale. In addition, structures and devices are shown schematically in order to simplify the drawing.
The terms “approximately”, “about” and “substantially” typically mean a value is within a range of +/−20% of the stated value, more typically a range of +/−10%, +/−5%, +/−3%, +/−2%, +/−1% or +/−0.5% of the stated value. The stated value of the present disclosure is an approximate value. Even there is no specific description, the stated value still includes the meaning of “approximately”, “about” or “substantially”.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It should be appreciated that, in each case, the term, which is defined in a commonly used dictionary, should be interpreted as having a meaning that conforms to the relative skills of the present disclosure and the background or the context of the present disclosure, and should not be interpreted in an idealized or overly formal manner unless so defined.
In addition, in some embodiments of the present disclosure, terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly (for example, electrically connection) via intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.
In the drawings, similar elements and/or features may have the same reference number. Various components of the same type can be distinguished by adding letters or numbers after the component symbol to distinguish similar components and/or similar features.
is a schematic diagram showing a power conversion circuit in accordance with an embodiment of the present invention. As shown in, the power conversion circuitis configured to convert an input voltage VIN into an output voltage VOUT, and includes a transformer TM, a resonant inductor LR, a resonant capacitor CR, an input capacitor CIN, a high-side transistor, a low-side transistor, a detection circuit, a feedback circuit, a control circuit, and a gate driving circuit.
The transformer TM includes a primary coil PS and a secondary coil SS, where the primary coil PS is coupled to a resonant node NR. The resonant inductor LR is coupled between the switch node SW and the primary coil PS, and the resonant capacitor CR is coupled between the resonant node NR and the ground. According to an embodiment of the present invention, the resonant inductor LR can be replaced by the leakage inductance of the primary coil PS of the transformer TM. In other words, the primary coil PS may be coupled between the switch node SW and the resonant node NR.
As shown in, the input capacitor CIN is coupled between the input voltage VIN and the ground. The high-side driving signal HS turns on and off the high-side transistorto provide the input voltage VIN to the switch node SW. The low-side driving signal LS drives the low-side transistorto be turned on and off, and couples the switch node SW to the ground. According to some embodiments of the present invention, the high-side transistorand the low-side transistorform a half-bridge circuit to drive the primary coil PS and the resonant capacitor CR.
The detection circuitis coupled to the resonant node NR to generate a current detection signal ICR and a voltage detection signal VCR. According to some embodiments of the present invention, the current detection signal ICR is configured to indicate the current flowing through the resonant capacitor CR, and the voltage detection signal VCR is configured to indicate the voltage across the resonant capacitor CR. According to an embodiment of the present invention, the detection circuitmay include a detection resistor (not shown in) coupled between the resonant capacitor CR and the ground, where the voltage across the detection resistor is the current detection signal ICR. According to another embodiment of the present invention, a capacitance voltage-dividing circuit formed by a first detection capacitor and a second detection capacitor (not shown in) may be coupled between the resonant capacitor CR and the ground to divide the voltage of the resonant node NR to generate a voltage detection signal VCR.
is a schematic diagram showing a detection circuit in accordance with an embodiment of the present invention. As shown in, the detection circuitincludes a first capacitor C, a first resistor R, and an integrator. The first capacitor Cand the first resistor Rare connected in series between the resonant node NR and the ground shown in, and the voltage across the first resistor Ris the current detection signal ICR. The integratorintegrates the current detection signal ICR to generate a voltage detection signal VCR, where the voltage detection signal VCR corresponds to the voltage of the resonant node NR. According to some embodiments of the present invention, the detection circuitcorresponds to the detection circuitin.
Returning to, the feedback circuitis configured to generate a compensation signal COMP based on the feedback voltage VFB and the reference voltage VREF. According to some embodiments of the present invention, the feedback voltage VFB is proportional to the output voltage VOUT. According to some embodiments of the present invention, the feedback circuitmay include an error amplifier, where the positive terminal of the error amplifier receives the reference voltage VREF, and the negative terminal receives the feedback voltage VFB. The feedback circuitcompares the feedback voltage VFB with the reference voltage VREF to generate a compensation signal COMP. It is illustrated that the compensation signal COMP is generated by utilizing the feedback voltage VFB herein, but the present invention is not intended to be limited thereto. According to other embodiments of the present invention, the feedback circuitmay also compare the output voltage VOUT with the reference voltage VREF to generate the compensation signal COMP.
According to some embodiments of the present invention, the feedback circuitgenerates a compensation signal COMP using the difference between the feedback voltage VFB and the reference voltage VREF, so that the output voltage VOUT reaches the target value when the feedback voltage VFB is equal to the reference voltage VREF. According to an embodiment of the present invention, when the feedback voltage VFB exceeds the reference voltage VREF, the feedback circuitreduces the compensation signal COMP. According to another embodiment of the present invention, when the reference voltage VREF exceeds the feedback voltage VFB, the feedback voltage increases the compensation signal COMP. According to an embodiment of the present invention, the feedback circuitmay include a voltage divider for dividing the output voltage VOUT to generate the feedback voltage VFB.
The control circuitgenerates an high-side gate-driving signal HSW and a low-side gate-driving signal LSW based on the current detection signal ICR, the voltage detection signal VCR, the compensation signal COMP, and the voltage of the switch node SW. The gate driving circuitgenerates a high-side driving signal HS based on the high-side gate-driving signal HSW, and generates a low-side driving signal LS based on the low-side gate-driving signal LSW.
As shown in, the power conversion circuitfurther includes a rectification circuit. The rectification circuitincludes a first rectification unit D, a second rectification unit D, and an output capacitor COUT. The first rectification unit Dis coupled between a first node Nof the secondary coil SS and the ground. The second rectification unit Dis coupled between the second node Nof the secondary coil SS and the ground. The output capacitor COUT is coupled between a middle node NC of the secondary coil SS and the ground, and an output voltage VOUT is generated at the middle node NC.
According to some embodiments of the present invention, the first rectification unit Dand the second rectification unit Drectify the energy of the secondary winding SS into the first current IDand the second current IDrespectively and provide them to the output capacitor COUT, thereby generating the output voltage VOUT. According to some embodiments of the present invention, the power conversion circuitmay be an LLC resonant power conversion circuit.
is a schematic diagram showing a control circuit in accordance with an embodiment of the present invention. As shown in, the control circuitincludes a first delay circuit, a first AND gate AND, a first flip-flop FF, a low-side conduction control circuit, a second flip-flop FF, and a first comparator CMPL.
The first delay circuitdelays the inverted low-side driving signal LSB, so that the first flip-flop FFenables the high-side gate-driving signal HSW based on the output signal of the first delay circuitand the clock signal CLK. When the compensation signal COMP generated by the feedback circuitofdoes not exceed the current detection signal ICR, the first comparator CMPresets the first flip-flop FFto disable the high-side gate-driving signal HSW. The low-side conduction control circuitsets or resets the second flip-flop FFbased on the inverted high-side gate-driving signal HSB (an inverse of the high-side gate-driving signal HSW), the voltage detection signal VCR, and the threshold voltage VTH, thereby generating the low-side gate-driving signal LSW and the inverted low-side gate-driving signal LSB.
is a waveform diagram showing a power conversion circuit in accordance with an embodiment of the present invention. The power conversion circuitofand the control circuitofwill be accompanied with the waveform diagram ofin the following paragraphs for detailed description. As shown in, in a switching cycle TSW, the high-side gate-driving signal HSW is first enabled at an initial time point t. At the first time point t, the current detection signal ICR exceeds the compensation signal COMP and the high-side gate-driving signal HSW is disabled. After the dead time, the low-side gate-driving signal LSW is enabled at the second time point t. According to an embodiment of the present invention, when the low-side transistoris turned on at the second time point t, zero-voltage switching (ZVS) can be achieved to reduce switching power loss. Then, the low-side gate-driving signal LSW is disabled at the third time point t, and the current detection signal ICR is zero from the third time point tto the fourth time point t, which means that the current flowing through the resonant capacitor CR is zero.
Unknown
November 20, 2025
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